Electric fuse.



GEORGE A. BRNHAM, OF SAUGUS, MASSACHUSETTS` ELEc'rnIc FUSE.

Specification o! Letters Patent.

Patented Sept. 11, 1917.

Application filed July 1, 1915. Serial No. 87,607.

To all lwhom t may concern.'

Be it known that I, GEORGE A. BURNHAM, a citizen of the United States, residing at Saugus, in the county of Essex and State of Massachusetts, have invented an Improvenient in Electric Fuses, of which the following is a specification.

This invention relates to electric fuses especially adapted to be arranged in polyphase circuits, for the protection of polyphase motors, to prevent them from running single phase, and has for its object the construction of a fuse comprising a lurality of fuse-strips, one for each phase o the circuit, all confined in an inclosing-case and insulated from each othcr,'portions of said strips being more or less closely associated tcgether in a common fusing izone, to form a short-circuiting means whereby the fusing of any one of the fuse-strips will result in the rupture ,of the adjacent strip or strips.

Another object is the rovision'of a small closed chamber at the using zones of the fuse-strips which will confine, atleast telnporarily, thcconducting gases produced by the fusing of any fuse-strip which conducting gases will short-circuit the adjacent strip or strips, causing them to rupture.

Another object is to rovide the fusestrips with reduced portions for insuring the fusing of the strips upon a given overload, and for localizing the fusing zone at the chamber aforesaid, and in'providing said strips with other reduced ortions for insuring the blowing ofthe use upon a greater overload and for localizing such blow-out at points outside of the chamber aforesaid, but Within the insulating inclosing-case.

Another object of the invention is the construction of an inclosing-case having a. middle partition-wall with a hole through which all of the fuse-strips extend, and other partition-walls arranged at each side Vof said middle wall by which the interior of the case is divided into compartments in which the end-portions of the fuse-strips are separately arranged.

Another object of the invention is the construction of an improved form of detachable clamping-means for the fuse-strips, which admits of their easy renewal.

Figure 1, is a plan view of a fuse embodying this invention, the cover of the inclosing-case being removed.

Flg. 2, is an underside plan view of cover.

Fig. 3, is a longitudinal vertical section of the fuse taken on the dotted line 3-3,

the

Fig: l.

ig. 4, is an yenlarged sectional detail of those portions of the fuse-strips which are closely associated together.

Fig. 5, is a sectional detail of one of the end connections of the fuse-strips.

The inclosing-case here shown is composed of any suitable insulating material, and cornprises essentially a bottom-wall 10, upright side walls 12, arranged on the bottom wall and within the Inarglns thereof at both ends, and a cover arranged on said side walls. A Ventilating cover is here shown comprising a top-plate 14 with numerous perforations 15, and un er-plates 16 and 17, arranged beneath it and separated from it a short distance to provide air-spaces between them, said under-plates being joined or otherwise connected with the top-plate at: their ends. These under-plates are usually arranged below the perforations. Within the box-like structure or case numerous partition-walls are arranged, as, for instance, there may be a middle partition-wall 20, extending from the bottom-Wall to or approximately flush with the top of the side-Wall, and there may be two diagonal partitionwalls arranged at each side of the partitionwall 20 which rise from the bottom-wall to or nearly to the top of the side-wall, said diagonal partition-walls being designated by reference characters 21, 22, 23 and 24. The partition-walls 21, 22, and likewise the partition-walls 23 and 24, converge and terminate near the middle partition-wall, and the walls of each pair are separated at their extremities to afford a space between them. The middle partition-wall has a hole through it directly 'in front of the spaces between the extremities of the diagonal partition walls.

The cover may have arranged on its underside a projection 25, arranged to fill a correspondingly shaped recess or void in the middle partition-wall, thus to complete said partion-Wall, and to assist in localizing the cover with respect to the case. With these several pa1'tition-\\alls arranged in the case, it will be observed that three separate rempart ments are provided, at cach side ot the middle imitiiQn-:val-lb 5 Within the case, as here shown, three fuse strips are arranged, as 30, fil and 32, although a greater or lesser number may be provided, in which instance the case will, be provided `with a correslionding number o'fv compartnients. 'lfhe fuse-strip 3Q,` is ai:- ranged' in two of the corner compartments, and extends through the hole in. the middle partition-wall, and hence is tortuously d isposed. The fuse-strip 32 is smilarlvarranged in the othertwo corner compartments, and likewise extends through the-h ole in the middle partition-wall andV is tortuously disposed.

The inse-strip 31:,is arranged in the two intermediate compartments and extends through the spaces between the extremities ofrthevwalls thereof',- andl through the hole in the middle partitionfwall.

As alli of the fuse-strips extendv through the saine. hole.in the midlle partition-Wall, it will beobserved that. theyare closely associated together along. such portions, but are sepaiiated and: insulated from each other;4 As al means ofl insulating the strips, thin strips orplatesof insulatingL material 35, 36, may'be arranged between them, that is to say, between. the. middle strip and the two sidestrips, and one ou more strips'of'insulatn ing-material 37 may be Wound' around allrof l the strips, bundling them together at their closely associated portions, and inclosing them in. a. sheath, all: as represented' in Fig. 4. Ati a middle point, each of thefusestrips and the insulating-strips 35, 3G, have a perforation, and all said perforations are disposed: in alinement, and: together form a closed chamber 38, see Eig. 4.

The fuse-stfrips each. have a recess 3Qv formed in.0ne or both ofrits edges at a point or. points beyond its middle portion, which substantially1 reduce. the. cross sectional a rea ofY thestuip, and upon reference to l? ig. l: these. reduced. portions are arranged in` the insulating compartment-s of the inclosingcase.

The reduction in. cross Sectional area. of the fuse-strips, Clue to the perfnrations formed therein, insures the fusing off any strips upon'a giveltover-load aml.`locali7.es. thefnsingmone at the middle, andthe alined: arrangement of the perforations, whereby. the chamber; 38 is formed, resultsy in. each conducting gases, which providea conduct ing pat-h betiween the fusedistrip anda-n adjacent strip, or strips, forminga short oirr cuit, whereupon such adiacenttstr-ip .or-strips.

togetherA with the. fusedistrip, will be caused' lo rupture at the reduced portions The reduction in cross sectional area of the fuse strips. due to the notches 39 insunes the bljoulingf of the fuse strips uponaA greater overload, and at such reduced places.

As anV illustration of an embodiment of my invention, take, for instance, a single tlneephase motor, supplied by a three-phase clrcuit, having a fuse in each phase or Wire udiichl protects the motor from overload,s\.1pr pose one of the fuses blows, from any cause, there is a sudden, increase of current in the other phases supplying the motor` which may not be of` sufiicientialue to blow, theremaining fuses, butv isor may be Qfsuiicient value to burn out; the motor after a relatively long period of: time, tlt'i'sbeing due to the fact thatl it is customary in supplying polyphase induction motorswi'th fuses, to select a fuse of a capacity greater than that which Will protect; the `motor on, overload, on` account of; the heavystart'ingcurrent required 'ior theinoton. Herein, when one of thefuse stripsuses, the gasfchambel; 3815ecomes filled with conducting-gases wl'iieh, provide a conductingpath-betiiieen the fused stripsI and' the other' fuse strips, forming a short circuithwheeeupon said fuse strips and one or both ofthe remainingfuse strips willl now blow at a higher overload at the-11e duced portions 39, and as-at^least two ofthe,

fuses-pwlilllglow in any event-,the motor will be-shut down. V

The ends ofthe flise-stripSa-re attached to suitable-connectors and2here'in a speciahfornr of-'connecboris shown, consisting-'cfa late 40, arranged outhe bottom-Wall' ontsi' e ot" the sidewallwhich extends through a slot'. in the side-wall', and* thel angularlyformed edge ofthe plate 4l, and th'otfher ear being arranged adjacent the-ear- 42andthe endof-I the use'strip is disposed between the ears 4Q` and.I 45, aiid' is held* frictionally by the clamping action; This form of\1 connector supports the fuse-strips entirely within the case-and admits of5 renewals of? the strips.

TheI fuse-is'electrically connected in circuit with thefusestrips separatelyarm nged in the several phases, The inelosingmase maybelled with any of` the Welllknown heat resisting materials commonly used i'n inelosedffuses, as-representedin Fig. 31

Ijy claimz- Y 1. An electric-fuse comprisingla plurality of separate fuse-strips insulated', fr0m each other, portionsoffthe strips beingclosely as sociatd tpgetherrto occupy positions inl the fusing zones of each` othen-to fomnshore circuiting. meanshfor the stri s, .and other portions being separated to orm blow-,out portions. I,

2. An electric-fuse comprising an` inclosing-case, a plurality of separate fuse-stripsV arranged in said case and insulated from each" othei", portions of" 'the strips being closely associated together to occupy positions in the fusing zonesofeach other to form short-circuitmg means 'for1 the strips, and other portions being separated to form blow-out,portionsl 3. An electric-fuse comprising an inclosing-case, a plurality of separate fuse-strips, some of which are tortuously arranged in said case and all of which are insulated from each other, portions of the strips being closely associated together to occupy positions in the fusing zones of each other to form short-circuiting means for the strips, and other portions being separated to form blow-out portions.

4. An electric-fuse comprising an inclosing-case, a plurality of separate fuse-strips arranged in said case and insulated from each other, and embedded in heat-resisting material, portions of the strips being closely associated to occupy positions in the fusing zones of each other to form short-eircuiting means for the strips, and other portions being seplzltrated to form blow-out portions.

5. electric-fuse comprising a plurality of separate fuse-strips, having associated fusing portions to form short-circuiting means for the strips, and widely separated blow-out portions insulated from each other.

6. An electric-fuse comprising a plurality of separate fuse-strips closely associated together at the fusing zones of each other, and thin spacing-pieces of insulating material arranged between said strips, and an insulating wrapper for the fuse-strips and spacingstrips.

7 An electric-fuse comprising a plurality of separate fuse-strips closely associated together at the fusing zones of each other, and perforated at such points, and spacing-pieces arranged between said strips having perforations arranged in alinement with the perforations in said strips, and an insulating Wrapper inclosing all of said strips and spacing-pieces, said alined perforations, together with the wrapper, forming a closed chamber.

8. An electric-fuse comprising a plurality of separate fuse-strips, insulated from each other, portions of the strips being closely associated together at their fusing zones and having alined perforations to form a closed chamber at such place for the gases caused by the fusing of any of the strips.

9. An electric-fuse comprising a plurality of separate fuse-strips insulated from each other, havin reduced portions at the middle and other reduced portions between the middle and the ends, portions of said strips, at the middle, being closely associated together, whereby the fusing of any fuse-strip, at the middle, will cause the blowing of the adjacent strip or strips.

l0. An electric-fuse comprising an inclosing-case of insulating material having a plurality o f compartments, and a middle partition wall with -a hole through it, a plurality of fuse-strips arranged in said case, portions of said strips extending through the hole in said middle partition wall and being closely associated together at such place to occupy positions in the fusing zones of each other, and other portions of said strips being arranged in the separate compartments of the case.

1l. An electric fuse comprising a plurality of fuse-strips, an inclosing-case for same having a middle partition-wall with a hole through it, through which all of the fusestrips extend, and partition-walls at each side of said middle wall arranged to form compartments at each side thereof, adapted to receive the end-portions of the strips, the portions of the strips which pass through the hole in the middle partition-Wall being closely associated together to form short-circuitinfg means for the strips upon the fusing o any strip, and thereby cause the endportions of the short-circuited strips to rupture.

12. An electric fuse comprising three fusestrips, an inclosing-case for same having a middle partition-wall with a hole through,

it, through which all of said fuse-strips extend, and diagonally-arranged partitionivalls at each side of said middle-wall arranged to form three compartments at each side of said middle-Wall adapted to receive the end-portions of the fuse-strips, the strips which pass through the hole in the middle partition-wall being closely associated together to form short-circuiting means for the strips upon the fusing of any strip, and thereby cause the end-portions of the shortcircuited strips to rupture.

13. An electric fuse comprising a plurality of fuse-strips, an inclosing-case for same having a middle partition-Wall with a hole through it, through which all of the fusestrips extend, diagonally-arranged partition- Walls at each side of said middle-wall which converge and terminate near the middle-Wall with a space between their converging ends, opposite the hole in the middle-Wall, to provide compartments adapted to receive the end-portions of the fuse-strips, the strips which pass through the hole in the middle pa rtition-wall being closely associated together to form short-circuiting means for the strips upon the fusing of any strip, and thereby cause the end-portions of the shortcircuited strips to rupture.

14. An electric fuse comprising a plurality of sepwrnite fuse-strips adapted for elecend-portions of the short-circuited-strips toy tnical connection with sepa/rate col'ld'uotors rupture.

oi? a multiple phase circuit, portions of said In testimony whereof, I have signedI my strips being el'esely associated together at name to this specification in the presence of 5' theifr fusing zone, said strips having aliied two subscribing witnesses.

per @rations to rm a chamber at their usi i V ing zonesadaiptedlto fuse the gases produced GDERGE A" BURNHAM upon the fusion A014' any strip, whlch ases Witnesses: l forma eomluetingl path to establish a s ort- E F'. LAWRENCE, M 10" cil-cuit for the strips and thereby cause the B. H. AHLERS.

Copies of this patent may be` obtained for five cents each, by addressing the Commissioner of Ptents.

i Washington, R1 01* 

